Vincent Dubroeucq

Visit your blog posts listing page, or a single post page, and open up the WordPress customizer.
Under Tiny Thumbnail Settings, choose or upload your default image. That’s it !
Enjoy !

Tiny Default Thumbnail

Allows you to add a default featured image to posts. Just add a default image in your customizer settings !

Freundschaft

This plugin adds a global default featured image and allows each category to define its own fallback image. When a post has multiple categories, the highest priority category fallback wins. If no category fallback applies, the global fallback is used.

Freundschaft Default Featured Images

Set a global default featured image and category-specific fallbacks with priority ordering.

Tiny Default Thumbnail vs Freundschaft Default Featured Images